I'm looking at fitting coilovers to my E46 M3 (Intrax 1K2) and want to make sure I strengthen the car appropriately. I know you guys are the top team for suspension setup so I have a quick question if I may:

On the front I am going to fit Turner Motorsport plates to the strut tower.
On the rear I am also going to fit Turner Motorsport plates to the shock tower.
I have a front strut brace already (standard M3 OEM).

And now for my question:

For the rear I think a strut brace would also add more material to the shock mounting point (as it is now going to support the weight of the car (being proper a coilover).

Do you think I should consider a rear strut that also braces to the rear subframe mounting points or would just a rear brace be fine with the rear coilovers?

You should consider the Subframe support. ( Not really Subframe support) more rear axle Carrierpanel support. You should consider it for longetivity of your car. That's a separate topic

With the true rear coilover I think you should certainly add a rear brace and reinforce the strut tower. If it was me I would just add the brace but that is because I have already done a rear axle Carrierpanel support brace. But if I didn't and had true rear coilovers I would like to kill two with the one stone and tie the strut tower into the Subframe brace.

The mason brace does indeed pick up the Subframe. The safety devices offer's nothing towards relieving the RACP and will only contribute to reinforcment of the strut tower.

If I were you , I would look into something that does both.

I saw a really nice brace on Facebook that is better than the mason brace and prob cheaper. I'll see if I can find a link. The reason it's better is because while it looks like the mason brace. Its connects to the chassis legs which the mason does not. This adds tremendous support and worth doing.

Edit.

Made by a crowd called " function". I like it because for your application it gets the turrets reinforcement and the chassis rail and picks up the Subframe offering load relief to the panel. It in America I think. Surely someone can copy it.

Thanks for your info schooner. When you say that the Mason brace picks up the subframe, but not the chassis leg, is that a big difference?

I'm probably opening a can of worms but does this mean taking the subframe off the car? Which would mean I might as well check for cracks, get any drilled out, and then fit plates too?

And should the front be strengthened further too!?

Could take quite a bit of effort before I actually fit the intrax kit.

It's a big difference in my book. The mason brace relies on the strut turrets to relieve the panel of the destructive flexion that pops the perimeter spot welds. This is not as effective as having a direct laterally projected bracket or flange or whatever it's called, which is in the same plane as the top of the rear mount bolt hole and the chassis leg is within 4-5 inches of that rear mount bolt hole. This is by far more efficient than how the mason brace would act.

To install the mason brace or any other similar brace you can certainly do it with the Subframe left in. You would need to remove exhaust and other things . And you would need a super long 10mm HSS drill bit to drill through into the boot space. But if you're going for this you should do it properly and fix and cracks and weld plates on at the same time.

Ah ok I see... the lateral load onto the side of the boot. You don't have a link to this bar do you, or another one which is just as good?

I copied the brave called the Vincebrace on m3forum. But this doesn't​address the turret reinforcment you need . So I think your best option is to do some research and visit a fabricator ( if you cannot do it yourself ). Show the picturew and take measurements and someone handy with a welder should be able to Knock something up for you easily enough.

That bar was made by someone called function . You could also buy the mason brace weld some chassis leg flanges like I circled above. Or as I said , just get something made up with some tubing. It's not rocket science to a fabricator.

I guess I could fit the coilovers and strut brace now and speak to a fabricator about a lower brace similar to your one? That would mean I could fit the coilovers now without too much fiddling, and then fit the subframe brace when I swap my diff for a 4.10 ratio?

I guess I could fit the coilovers and strut brace now and speak to a fabricator about a lower brace similar to your one? That would mean I could fit the coilovers now without too much fiddling, and then fit the subframe brace when I swap my diff for a 4.10 ratio?

Yea I guess that is a plan. Because the exhaust is coming down then anyway.